/*
 * Copyright (C) 2015 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import java.util.concurrent.Future;

/**
 * Computes a value, possibly asynchronously. For an example usage and more information, see
 * {@link Futures.FutureCombiner#callAsync(AsyncCallable, java.util.concurrent.Executor)}.
 *
 * <p>
 * Much like {@link java.util.concurrent.Callable}, but returning a {@link ListenableFuture} result.
 *
 * @since 20.0
 */
@Beta
@GwtCompatible
public interface AsyncCallable<V> {
    /**
     * Computes a result {@code Future}. The output {@code Future} need not be
     * {@linkplain Future#isDone done}, making {@code AsyncCallable} suitable for asynchronous
     * derivations.
     *
     * <p>
     * Throwing an exception from this method is equivalent to returning a failing
     * {@link ListenableFuture}.
     */
    ListenableFuture<V> call() throws Exception;
}
